The invention relates to a method of processing a multiphase well effluent mixture.
Such a method is known from OTC paper 17399 “Subsea Gas Compression—Challenges and Solutions” presented by R. Fantoft at the Offshore Technology Conference held in Houston, USA on 2-5 May 2005 and from International patent applications WO03/033870 WO03/035335 and WO2005/026497. The method known from WO2005/026497 comprises:                transferring the multiphase well effluent mixture via a multiphase well effluent flowline to a gas liquid separator in which the multiphase well effluent mixture is separated into substantially gaseous and liquid fractions;        transferring the substantially liquid fraction into a liquid flowline in which a liquid pump is arranged;        transferring the substantially gaseous fraction into a gas flowline in which a gas compressor is arranged;        protecting the gas compressor against liquid surges by recirculating a recycled gas stream via a gas recycling conduit through the gas compressor in response to detection of a liquid surge in the multiphase well effluent mixture.        
In the method known from WO2005/026497 the recycled gas is heated up each time when it is compressed in the gas compressor and subsequently cooled in a heat exchanger arranged in the gas recycling conduit. Such a heat exchanger is a large piece of equipment because heat conductivity of the recycled gas is small, so that a large heat exchanging surface is required to cool the recycled gas stream to such a temperature that overheating of the gas compressor is prevented.
In the known method liquid in the liquid flowline may be cooled and recycled into the multiphase well effluent flowline, but in case the well effluents are substantially liquid, then the gas compressor may be substantially solely fed with recycled gas, so that the influx of substantially liquid well effluents and of recycled cooled liquid is inhibited.
It is an object of the present invention to provide an improved method of processing a multiphase well effluent mixture, wherein the processing involves the use of a compact fluid separation and pressure boosting assembly. It is a further object of the present invention to provide an improved method of processing a multiphase well effluent mixture in which a gas compressor is protected against pressure and/or liquid surges and overheating by using a gas recirculating conduit, in which the need for a bulky gas-liquid heat exchanger in the gas recycling conduit is obviated.